Overview

This FOSDEM 2024 slide deck presents OpenTimestamps, an open protocol and reference infrastructure for creating and verifying cryptographic timestamps that prove a piece of data existed at or before a specific point in time. Originally designed by Peter Todd, OpenTimestamps minimizes trust by never requiring a central timestamping authority: instead it hashes data, aggregates many independent hashes through public calendar servers, and periodically commits the aggregated Merkle root to the Bitcoin blockchain. Because verification ultimately depends only on Bitcoin’s public ledger, timestamp proofs remain checkable by anyone, indefinitely, and offline once the blockchain commitment is present.

Key points

• Proof of existence, not authorship or creation: a timestamp shows data existed no later than a given block time, deriving its trust from Bitcoin rather than from any operator.
• Hash-first design: only the SHA-256 (or similar) digest of a file is submitted, so the original content stays private and proofs stay compact.
• Calendar servers aggregate: public calendar servers collect submissions from many users and batch them into a single Merkle tree, so one Bitcoin transaction can timestamp an effectively unbounded number of documents at negligible marginal cost.
• Two-phase workflow: submission returns an incomplete proof pointing at a calendar; after the calendar’s root is committed on-chain (roughly Bitcoin’s block cadence), the proof is upgraded to include the full path down to a confirmed block.
• Independent verification: a completed .ots proof is a self-contained chain of hash operations and a Merkle path leading to a Bitcoin block header, so verifiers need only the blockchain, not the calendar or its operator.
• Use cases highlighted include document authentication, legal and evidentiary records, regulatory compliance, and supply-chain or provenance verification.

Relevance to Truestamp

OpenTimestamps and Truestamp share the same core primitives: hashing input data, aggregating many items into an RFC 6962 style Merkle tree, and recording a root on public infrastructure to prove data preceded that record. Truestamp likewise frames its guarantee as a submission window rather than a claimed creation time, and its proof lifecycle parallels the OpenTimestamps upgrade step where an incomplete proof becomes fully verifiable once the block commitment lands on a public chain such as Bitcoin.

Citations

1. Timestamping with OpenTimestamps, FOSDEM 2024. FOSDEM 2024 conference slide deck (event 3661); OpenTimestamps protocol originally designed by Peter Todd.